Immediately exploiting the problems with Black's last move.
2... f7f5 Now White shouldn't play 3.Nb5 as Black can take on a2. 3. a1b3  3... b8a6 Caruana keeps the c7-pawn protected. 4. d2d3  4... c7c6 Forever preventing Nb5, but the position of the knight on b6 is weakened.